Sverdrup Basin Carboniferous Rift Sedimentation and Linkages to Ellesmerian Basement Structures, SW Ellesmere Island
Benoit Beauchamp1 and Pierre Theriault2
1Department of Geoscience, University of Calgary, Calgary, AB, Canada.
2Statoil, Stavanger, Norway.
A new geological compilation of Upper Paleozoic formations and related structural elements in the Blind Fiord and Trold Fiord area, SW Ellesmere Island, has allowed us to reconstruct the Sverdrup Basin's rift-related history of the area and establish linkages with the underlying Ellesmerian structures in spite of locally severe Tertiary overprinting. Immediately east of Trold Fiord, the Ellesmerian Orogeny led to symmetrical thrust-bounded folds that developed above a principal décollement surface within the Ordovician Baumann Fiord Formation. A long east-verging overturned syncline lies along the axis of Trold Fiord and involves strata as young as the Devonian Danish River Formation. The western limb of the syncline is overthrusted by the Ordovician Thumb Mountain and Irene Bay formations, which form a tightly folded, highly contorted and several times repeated beam of carbonates. Following peneplanation of the Ellesmerian Orogen, two large down-to-the-basin half-grabens developed along NNE-trending master listric faults. The bounding fault of the North Trold Fiord Depression (NTFD) lies a few kms east of the head of Trold Fiord. Excellent exposures of the Bashkirian to mid-Moscovian syn-rift graben fill occur immediately west of the head of Trold Fiord. Red weathering conglomerates and sandstones (Lower clastic member, Canyon Fiord Formation) representing alluvial fan and stream flood deposits within a series of transverse east-west incised valleys were derived from the hangingwall uplift of Thump Mountain-Irene Bay carbonates to the west. Fluvial sandstones occurred in the more distal graben-axial area to the east. Marine transgression followed, with marine sandstones progressively giving way to marine carbonates. The sea progressively flooded the area occupied by both the footwall and hangingwall highs. By mid-Moscovian time, fault-related subsidence ceased and carbonates prograded extensively basinward (Middle limestone member, Canyon Fiord Formation). The West Trold Fiord Depression (WTFD) lies south and west of the NTFD and its NNE-trending bounding fault is on the west side of Trold Fiord. A thick succession of alluvial fan and braided stream conglomerates is exposed to the west, the debris of which were derived from the eroded Ellesmerian stack of Ordovician carbonates that forms the footwall uplift to the east. The sea rapidly invaded the WTFD and non-marine conglomerates were rapidly replaced by marine limestones and subaqueous evaporites. Both the NTFD and WTFD half-grabens were partially exhumed through several Early Permian inversion pulses collectively termed the Melvillian Disturbance. Regional uplift and reactivation of Ellesmerian thrusts occurred during the Tertiary Eurekan Orogeny. Dextral strike slip separation along Trold Fiord Thrust has resulted in the western half of the WTFD being now located some 15-18 kms north of its eastern half.
AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.